Processing thoughts is an attempt to connect thoughts together in meaningful ways to form new insights.
This necessarily means that processing one’s thoughts means processing emotions and feelings as well as ideas.
Emotions and feelings present a unique challenge in that in order to properly process them, the feelings need to be acknowledged, validated, and felt.
Once the feelings are accepted, they can be processed using tools such as journaling.
A Zettelkasten, on the other hand, is effective at processing ideas.